Technical Field
This Patent Document relates generally to rotational sensing for angle, frequency, direction, such as used for sensing motor (generator) rotation.
Related Art
Electric motors include a rotor that rotates within a stationary stator. Either the rotor or stator is formed with permanent magnets, and the other component is formed with current-carrying windings. As an example, stepper motors typically use a magnetic rotor with stator windings.
In implementations where the rotor is formed of magnetic material, motor current drive to the stator windings generates a rotating magnetic field that completes one revolution in one cycle of the stator currents, with a rotor angular velocity that depends on the frequency of the current drive.
Motor drive systems can be designed for adjustable speed control, and bi-directional motor rotation. Providing motor control requires some system for sensing motor rotation information, such as rotational frequency, angle and direction. However, rotational sensing systems for stepper and other motor applications are susceptible to EMI (electromagnetic interference) from the stator magnetic field coupled into the sensing system.
While this Background information is presented in the context of electric motors, the present Disclosure is not limited to such applications, but is more generally directed to rotational sensing for angle, frequency and direction.